Technology Today Volumn 3 Issue 1 - Raytheon


Technology Today Volumn 3 Issue 1 - Raytheon

(less than 20 KHz) to visible light (30,000

GHz — or 30 Terahertz).

The wide-ranging variety of functions that

together represent the science of RF signaling

include the following:

• RF frequency synthesis and waveform


• RF signal amplification and processing

• Electromagnetic wave radiation and

reception to free-space — via antennas

• Signal and frequency detection

• Information coding and decoding

• Atmospheric propagation and

reflection to/from objects

The range of technologies used to implement

and build these functions is broader

still, extending from tubes to exotic semiconductors,

antennas to lenses, and waveguides

to photonic interconnects. Common

uses of RF Waves include communications,

direction-finding, geo-location, radar, passive

signal detection and classification,

remote sensing/radio astronomy, RF heating

and welding.

Raytheon’s range of RF Systems can be

grouped into four basic functional categories

as follows (although other specialized

uses may also be developed):

• Radars designated for airborne,

missile, ground, space, battlefield,

shipboard, remote sensing and airtraffic-control


• Radio communications systems, data

links and satellite terminals

• Electronic Warfare (EW) and Signal

Intelligence and

• GPS and Navigation systems


Active RF Sensors

In the autumn of 1922, the US Naval

Research Laboratory (NRL) first detected a

moving ship using radio waves. Eight years

later, NRL similarly discovered that reflected

radio waves directed at aircraft could be

detected. In 1934, a patent was granted to

Taylor, Young, and Hyland at NRL for a

“System for Detecting Objects By Radio.”

The term given to this new science was

Radar (standing for Radio Detection And

Ranging). In other countries around the

world, similar discoveries and inventions of

radars were occuring. Early radar concepts

and experiments performed at NRL in the

U.S. focused on the detection of ships and,

later, aircraft. Early radars were primarily

used for direction finding via radio-location

(an early name for radar). Later, pulsed CW

techniques were added to perform target

ranging, employing a round polar display

with a rotating arc sweep marker, as popularized

in movies and TV.

Since those early days, Raytheon and its

subsidiary companies had a long history in

the ongoing development of radar for military

and commercial applications. Founded

in 1922, Raytheon came into prominence

early in the Second World War when Percy

Spencer, a Raytheon engineer, developed a

method for volume production of highquality

Magnetron tubes which are critical

to radar operation (and microwave ovens).

Raytheon,and its acquired components

from E-Systems, Hughes Aircraft, Texas

Instruments and General Dynamics all have

a long history in radar sensors which are

currently integrated into nearly every conceivable

platform — on land, sea, air and

space — including strike fighters, bombers,

AWACs, Unmanned Air Vehicles (UAVs) and

commercial aircraft. Add to that a long list

of Naval ships and systems, commercial

marine ships/personal watercraft, ballistic

missile defense ground systems, battlefield

defense and targeting systems, missile seekers,

automobiles and satellites, etc.

Altimeters and direction finders are also

forms of radar sensors.

Though most radars are active (in that they

send out a signal to illuminate a target and

detect the reflected signal similar to shining

a light on an object in the dark), some

radar sensors are passive (in that they do

not illuminate the targets, but measure the

targets’ natural energy and/orsignal emissions).

One of these systems — referred to

as radiometers — are often used on spacecraft

to gather information about water, on

and above the Earth, through passive

receivers at various microwave and millimeter

wave frequencies. These systems

observe atmospheric, land, oceanic and

cryospheric (or frozen mass) parameters,

including precipitation, sea surface temperatures,

ice concentrations, snow water

equivalent, surface wetness, wind speed,

atmospheric cloud water and water vapor.

Shipboard Radar

The days of Navy surface combatants only

patrolling the high seas and engaging

threats at close range are past. Today’s surface

combatants perform a variety of missions,

operating in both deep water and

the ‘littorals’ (continental shelf), and must

counteract a variety of ever-increasing

threats. Current shipboard radar systems

operating over a wide range of RF frequencies

provide the capabilities to successfully

carry out these missions. Because current

radar systems typically perform a single or

limited number of mission functions, the

surface warship is host to a number of

independent shipboard radar systems. This

host of radar systems aboard a single ship

can lead to a significant degree of RF interference

between radars, communications

and electronic warfare systems. To reduce

these effects, system and frequency management,

filtering and high-linearity

receivers are an integral part of today’s

advanced weapon systems.

The types of radar systems aboard a ship

are strictly a function of the vessel’s class or

category. As an example, a precision

Continued on page 6


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